Bio-separation describes techniques used for determining the molecular state of a cell, or whole organism. Currently, bio-separation is often performed using liquid chromatography, electrophoresis or centrifugation, which achieves separation by transporting an analyte relative to a stationary phase based on a physical or chemical property, such as surface chemistry, size, charge, or mass density. Although these techniques are able to separate analytes with a high resolution they are slow and often difficult to implement. For example, when screening for sexually transmitted infections (STIs) rapid diagnosis is critical as delays can lead to progression of chronic disease, infertility, cancer, and contribute to continued pathogen and disease transmission. Point of care testing for some STIs can often be difficult as antigens are often present at levels below the current sensitivity of point of care testing technologies, and samples can often require pre-treatment involving purification or filtration. This ultimately leads to an analysis time that takes longer than is acceptable. Assays that measure fluorescence or light scattering have been provided. To operate such an assay it is typically necessary that the assay beads be functionalized with additional materials to provide a basis for measurement. Such systems do not have the capacity to provide a quantitative measurement of specific particles. Typically such systems are directed to providing only an indication that a specific particle is present. Techniques such as light scattering respond non-linearly to different size particles. It is not possible to use such approaches to count individual particles. Other aggregation assay methods have relied upon two main modes of detection—monitoring the aggregation as a function of analyte concentration measuring chain length or turbidity, monitoring a change in magnetic properties as particles are forced to be in close proximity to each other. Such techniques have a limited dynamic range and are difficult to multiplex. In biosensing there is a need for improved detection systems that operate with short analysis time and provide improved accuracy of measurement of analytes. There is further a need for improved point of care testing systems that are robust and easy to operate.
There is therefore a need to address these and other problems and limitations of prior art separation devices and methods. There is a need to for a more efficient and reliable and sensitive assay method and approach that addresses the above noted problems.